fix: report valid color lookup values clearly

src/machinevisiontoolbox/base/color.py

@@ -963,20 +963,20 @@ def XYZ2RGBxform(
     if isinstance(white, str):
         try:
             white_xy = np.array(_whites[white.lower()])
-        except:
+        except KeyError as exc:
             raise ValueError(
-                "unknown white value, must be one of" ", ".join(_whites.keys())
-            )
+                f"unknown white value, must be one of {', '.join(_whites)}"
+            ) from exc
     else:
         white_xy = smb.getvector(white, 2)
 
     if isinstance(primaries, str):
         try:
             primary_xy = _xy_primaries[primaries.lower()]
-        except:
+        except KeyError as exc:
             raise ValueError(
-                "unknown primary value, must be one of" ", ".join(_xy_primaries.keys())
-            )
+                f"unknown primary value, must be one of {', '.join(_xy_primaries)}"
+            ) from exc
     else:
         primary_xy = smb.getmatrix(primaries, (3, 2))
 

tests/test_color_lookup_errors.py

@@ -0,0 +1,24 @@
+import unittest
+
+from machinevisiontoolbox.base.color import XYZ2RGBxform
+
+
+class TestColorLookupErrors(unittest.TestCase):
+    def test_unknown_white_lists_supported_values(self):
+        """Report supported white points once, separated by commas."""
+        with self.assertRaises(ValueError) as raised:
+            XYZ2RGBxform(white="unknown")
+        self.assertEqual(
+            str(raised.exception), "unknown white value, must be one of d65, e"
+        )
+        self.assertIsInstance(raised.exception.__cause__, KeyError)
+
+    def test_unknown_primaries_lists_supported_values(self):
+        """Report supported primaries once, separated by commas."""
+        with self.assertRaises(ValueError) as raised:
+            XYZ2RGBxform(primaries="unknown")
+        self.assertEqual(
+            str(raised.exception),
+            "unknown primary value, must be one of itu-709, cie, srgb",
+        )
+        self.assertIsInstance(raised.exception.__cause__, KeyError)